JSP如何調用Web服務

在JSP中調用Web服務，可以使用多種方法。這里，我將向您展示如何使用java.net.HttpURLConnection和javax.xml.ws.handler.MessageContext來實現這一目標。

方法1：使用java.net.HttpURLConnection

<%@ page import="java.io.BufferedReader" %>
<%@ page import="java.io.InputStreamReader" %>
<%@ page import="java.net.HttpURLConnection" %>
<%@ page import="java.net.URL" %>

<%
    try {
        // 替換為您的Web服務URL
        String webServiceUrl = "https://example.com/webservice";
        URL url = new URL(webServiceUrl);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        connection.setRequestProperty("Content-Type", "application/json; utf-8");
        connection.setRequestProperty("Accept", "application/json");
        connection.setDoOutput(true);

        int responseCode = connection.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String inputLine;
            StringBuilder response = new StringBuilder();

            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();

            // 輸出響應
            out.println("Response: " + response.toString());
        } else {
            out.println("GET request failed");
        }
    } catch (Exception e) {
        e.printStackTrace();
        out.println("Error: " + e.getMessage());
    }
%>

方法2：使用javax.xml.ws.handler.MessageContext

首先，您需要生成Web服務的客戶端代理類。您可以使用Apache CXF、JAX-WS或Eclipse IDE等工具生成客戶端代碼。這里假設您已經生成了名為MyWebServiceService的服務接口和MyWebService的服務實現類。

<%@ page import="javax.xml.ws.BindingProvider" %>
<%@ page import="com.example.MyWebServiceService" %>
<%@ page import="com.example.MyWebService" %>

<%
    try {
        // 創建Web服務客戶端代理
        MyWebServiceService service = new MyWebServiceService();
        MyWebService port = service.getMyWebServicePort();

        // 設置請求上下文
        BindingProvider bindingProvider = (BindingProvider) port;
        MessageContext messageContext = bindingProvider.getRequestContext();
        messageContext.put("http.request.headers", Collections.singletonMap("Content-Type", Collections.singletonList("application/json")));

        // 調用Web服務方法
        String response = port.myWebServiceMethod();

        // 輸出響應
        out.println("Response: " + response);
    } catch (Exception e) {
        e.printStackTrace();
        out.println("Error: " + e.getMessage());
    }
%>

請注意，這些示例僅用于演示目的。在實際應用中，您可能需要根據具體需求對代碼進行調整。